Replication in E. coli is
Initiation at oriC recruits two DnaB helicases loading onto opposite parental strands, each advancing outward in opposite directions from origin. Replication then proceeds bidirectionally with two forks moving away from origin toward terminus region opposite chromosome. Bidirectional synthesis doubles overall speed of genome duplication and is typical of bacterial archaeal and eukaryotic chromosomes. Unidirectional replication occurs in some plasmids via rolling circle mechanism but not chromosome. Bidirectionality explains bubble structures observed in electron micrographs and timing of genet
Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 11: Bidirectional replication from oriC origin
